Incident Overview
A medical helicopter crew and pilot completed a patient transport to a rooftop hospital helipad. Following the patient offload with the engines running, the ground crew gave a "thumbs up" indicating that the helicopter's doors were secure and all equipment had been stowed. The pilot then completed the before-takeoff checklist, but overlooked disengaging the cyclic control lock mechanism, which had been used to secure items placed on the front left seat during the flight.
Sequence of Events
As the pilot pulled the collective pitch lever and the helicopter began to lift off and move rearward, he realized the cyclic control lock was still engaged. Fearing the backward movement might carry the helicopter over the helipad edge, he immediately lowered the collective pitch, resulting in a hard landing.
Post-Incident Findings
Examination of the cyclic stick locking mechanism revealed that it was non-contrasting and dark gray in color. The manufacturer had produced three color schemes: light gray, black, and light gray with a yellow tip. Prior to the incident, a service bulletin had recommended painting the end of older locking mechanisms yellow to provide contrast; subsequent production models included a light gray and yellow mechanism.
The locking pin was secured under the instrument panel and designed to shear through with a jerky movement if not unlocked, requiring approximately 26.98 pounds of force at the stick grip. However, the pilot reported that despite attempting to jerk the stick, he could not disengage the lock. Post-incident tests measured the breakout force at around 44 pounds in one test and 42 pounds in another.
Additionally, the operator's checklist for the helicopter did not reference the cyclic stick locking mechanism or include a requirement to verify that flight controls were free and correct. The company's operations manual also did not address use of the locking mechanism during hot loading or unloading.